Liquid-crystalline medium and liquid-crystal display comprising the same

ABSTRACT

The invention relates to a liquid-crystalline medium, preferably having a nematic phase and negative dielectric anisotropy, which comprises
         a) one or more compounds of formula I       

     
       
         
         
             
             
         
       
         
         
           
             and 
             b) one or more compounds selected from the group of compounds of the formulae II and III 
           
         
       
    
     
       
         
         
             
             
         
       
     
     in which the parameters have the respective meanings indicated in claim  1 , to the use thereof in an electro-optical display, particularly in an active-matrix display based on the VA, ECB, PALC, IPS or FFS effect, to displays of this type which contain a liquid-crystalline medium of this type, and to the use of the compounds of formula I for reduction of the dispersion of the birefringence of a liquid-crystalline medium which comprises one or more compounds of the formulae II and/or III.

The present invention relates to novel liquid crystalline media, inparticular for use in liquid-crystal displays, and to theseliquid-crystal displays, particularly to liquid-crystal displays whichuse the ECB (electrically controlled birefringence) effect, the IPS(in-plane switching) or the FFS (fringe field switching) effect, bothwith dielectrically negative liquid crystals. The last one is alsocalled UB-FFS (ultra bright FFS) effect occasionally. For the firsteffect the dielectrically negative liquid crystals are used in ahomeotropic initial alignment and the latter two in a homogeneous (i.e.planar) initial alignment. The liquid-crystal media according to theinvention are distinguished by a particularly small wavelengthdispersion of the birefringence. This also leads to small colour shiftin the displays according to the invention.

The principle of electrically controlled birefringence, the ECB effector DAP (deformation of aligned phases) effect, was described for thefirst time in 1971 (M. F. Schieckel and K. Fahrenschon, “Deformation ofnematic liquid crystals with vertical orientation in electrical fields”,Appl. Phys. Lett. 19 (1971), 3912). Papers by J. F. Kahn (Appl. Phys.Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44(1973), 4869) followed.

The papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers(1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82Digest Techn. Papers (1982), 244) have shown that liquid-crystallinephases must have high values for the ratio between the elastic constantsK₃/K₁, high values for the optical anisotropy Δn and values for thedielectric anisotropy Δ∈ of ≦−0.5 in order to be suitable for use forhigh-information display elements based on the ECB effect.Electro-optical display elements based on the ECB effect have ahomeotropic surface alignment (VA technology=vertically aligned).Dielectrically negative liquid-crystal media can also be used indisplays which use the so-called IPS (in-plane switching) effect.

According to the present application, however, the IPS or the FFS effectwith dielectrically negative liquid crystals in a homogeneous alignmentare preferred.

Industrial application of this effect in electro-optical displayelements requires LC phases which have to meet a multiplicity ofrequirements. Particularly important here are chemical resistance tomoisture, air and physical influences, such as heat, radiation in theinfrared, visible and ultraviolet regions, and direct (DC) andalternating (AC) electric fields.

Furthermore, LC phases which can be used industrially are required tohave a liquid-crystalline mesophase in a suitable temperature range andlow viscosity.

None of the series of compounds having a liquid-crystalline mesophasethat have been disclosed hitherto includes a single compound which meetsall these requirements. Mixtures of two to 25, preferably three to 18,compounds are therefore generally prepared in order to obtain substanceswhich can be used as LC phases.

Matrix liquid-crystal displays (MLC displays) are known. Non-linearelements which can be used for individual switching of the individualpixels are, for example, active elements (i.e. transistors). The term“active matrix” is then used, where in general use is made of thin-filmtransistors (TFTs), which are generally arranged on a glass plate assubstrate.

A distinction is made between two technologies: TFTs comprising compoundsemiconductors, such as, for example, CdSe, or TFTs based onpolycrystalline and, inter alia, amorphous silicon. The lattertechnology currently has the greatest commercial importance worldwide.

The TFT matrix is applied to the inside of one glass plate of thedisplay, while the other glass plate carries the transparentcounterelectrode on its inside. Compared with the size of the pixelelectrode, the TFT is very small and has virtually no adverse effect onthe image. This technology can also be extended to fully colour-capabledisplays, in which a mosaic of red, green and blue filters is arrangedin such a way that a filter element is located opposite each switchablepixel.

The TFT displays most used hitherto usually operate with crossedpolarisers in transmission and are backlit. For TV applications, ECB (orVAN) cells or FFS cells are used, whereas monitors usually use IPS cellsor TN (twisted nematic) cells, and notebooks, laptops and mobileapplications usually use TN, VA or FFS cells.

The term MLC displays here encompasses any matrix display havingintegrated non-linear elements, i.e., besides the active matrix, alsodisplays with passive elements, such as varistors or diodes(MIM=metal-insulator-metal).

MLC displays of this type are particularly suitable for TV applications,monitors and notebooks or for displays with a high information density,for example in automobile manufacture or aircraft construction. Besidesproblems regarding the angle dependence of the contrast and the responsetimes, difficulties also arise in MLC displays due to insufficientlyhigh specific resistance of the liquid-crystal mixtures [TOGASHI, S.,SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E.,WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp. 141 ff.,Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of ThinFilm Transistors for Matrix Addressing of Television Liquid CrystalDisplays, pp. 145 ff., Paris]. With decreasing resistance, the contrastof an MLC display deteriorates. Since the specific resistance of theliquid-crystal mixture generally drops over the life of an MLC displayowing to interaction with the inside surfaces of the display, a high(initial) resistance is very important for displays that have to haveacceptable resistance values over a long operating period.

Displays which use the ECB effect have become established as so-calledVAN (vertically aligned nematic) displays, besides IPS displays (forexample: Yeo, S. D., Paper 15.3: “An LC Display for the TV Application”,SID 2004 International Symposium, Digest of Technical Papers, XXXV, BookII, pp. 758 and 759) and the long-known TN displays, as one of the threemore recent types of liquid-crystal display that are currently the mostimportant, in particular for television applications.

The most important designs may be mentioned here: MVA (multi-domainvertical alignment, for example: Yoshide, H. et al., Paper 3.1: “MVA LCDfor Notebook or Mobile PCs . . . ”, SID 2004 International Symposium,Digest of Technical Papers, XXXV, Book I, pp. 6 to 9, and Liu, C. T. etal., Paper 15.1: “A 46-inch TFT-LCD HDTV Technology . . . ”, SID 2004International Symposium, Digest of Technical Papers, XXXV, Book II, pp.750 to 753), PVA (patterned vertical alignment, for example: Kim, SangSoo, Paper 15.4: “Super PVA Sets New State-of-the-Art for LCD-TV”, SID2004 International Symposium, Digest of Technical Papers, XXXV, Book II,pp. 760 to 763) and ASV (advanced super view, for example: Shigeta,Mitzuhiro and Fukuoka, Hirofumi, Paper 15.2: “Development of HighQuality LCDTV”, SID 2004 International Symposium, Digest of TechnicalPapers, XXXV, Book II, pp. 754 to 757). More modern versions of the VAeffect, are the so called PAVA (photo-alignment VA) and PSVA(polymer-stabilized VA).

In general form, the technologies are compared, for example, in Souk,Jun, SID Seminar 2004, Seminar M-6: “Recent Advances in LCD Technology”,Seminar Lecture Notes, M-6/1 to M-6/26, and Miller, Ian, SID Seminar2004, Seminar M-7: “LCD-Television”, Seminar Lecture Notes, M-7/1 toM-7/32. Although the response times of modern ECB displays have alreadybeen significantly improved by addressing methods with overdrive, forexample: Kim, Hyeon Kyeong et al., Paper 9.1: “A 57-in. Wide UXGATFT-LCD for HDTV Application”, SID 2004 International Symposium, Digestof Technical Papers, XXXV, Book I, pp. 106 to 109, the achievement ofvideo-compatible response times, in particular in the switching of greyshades, is still a problem which has not yet been solved to asatisfactory extent.

ECB displays, like ASV displays, use liquid-crystalline media havingnegative dielectric anisotropy (Δ∈), whereas TN and to date allconventional IPS displays use liquid-crystalline media having positivedielectric anisotropy. However, presently there is an increasing demandfor IPS and FFS displays utilizing dielectrically negative liquidcrystalline media.

In liquid-crystal displays of this type, the liquid crystals are used asdielectrics, whose optical properties change reversibly on applicationof an electrical voltage.

Since in displays in general, i.e. also in displays in accordance withthese mentioned effects, the operating voltage should be as low aspossible, use is made of liquid-crystal media which are generallypredominantly composed of liquid-crystal compounds, all of which havethe same sign of the dielectric anisotropy and have the highest possiblevalue of the dielectric anisotropy. In general, at most relatively smallproportions of neutral compounds and if possible no compounds having asign of the dielectric anisotropy which is opposite to that of themedium are employed. In the case of liquid-crystal media having negativedielectric anisotropy for ECB displays, predominantly compounds havingnegative dielectric anisotropy are thus employed. The liquid-crystalmedia employed generally consist predominantly and usually evenessentially of liquid-crystal compounds having negative dielectricanisotropy.

In the media used in accordance with the present application, at mostsignificant amounts of dielectrically neutral liquid-crystal compoundsand generally only very small amounts of dielectrically positivecompounds or even none at all are typically employed, since in generalthe liquid-crystal displays are intended to have the lowest possibleaddressing voltages.

WO 2009/021671 discloses a dielectrically negative liquid crystallinemedium, which comprises a compound of formula

WO 2012/076105 discloses dielectrically negative liquid crystallinemedia, which may comprises e.g. compounds selected from of the followingformulae

For many practical applications in liquid-crystal displays, however, theknown liquid-crystal media do not show a sufficiently low dispersion ofthe birefringence, i.e. a small dependence of the values of both n_(e)and, in particular, Δn on the wavelength of the light used, especiallyin the visible range of the spectrum.

Much work has already been invested to practical and theoretical studiesof the birefringence dispersions of liquid crystals and their influenceon certain electro-optical effects. Some illustrative publications aree.g.

-   Wu, Sin-Tson: “Birefringence dispersions of liquid crystals”, Phys.    Rev. A, Vol. 33, No. (2), (1986), pp. 1270-1274;-   Breddels, P. A., van Sprang, H. A., and Bruinink, J.: “Influence of    dispersion on the transmission characteristics of supertwisted    nematic effects in liquid-crystal displays”, J. Appl. Phys., Vol.    62, No. (5), (1987), pp. 1964-1967;-   Wu, Shin-Tson: “A semi-empirical model for liquid-crystal refractive    index dispersions”, PACS#61.30.-V, 78.20.Ci, 78.40.-q.;-   Wu, Shin-Tson and Wu, Chiung-Seng: “A three-band model for    liquid-crystal birefringence dispersion”, J. Appl. Phys. Vol. 66,    No. (11), (1989), pp. 5297-5301; and-   Abdulahim, I.: “Dispersion Relations for the Refractive Indices and    the Effective Birefringence of Liquid Crystals”, Mol. Cryst. Liq.    Cryst., Vol. 197, (1991), pp. 103-108.

The liquid-crystal media of the prior art having correspondingly lowaddressing voltages have relatively low electrical resistance values ora low VHR and often result in undesired shift in colour balance uponobservation from an oblique viewing angle. This e.g. leads for displayed“white” colour to a yellowish hue, when the display is viewed from anoblique angle. This problem is due in part to the relatively largewavelength dispersion of the birefringence values of conventional liquidcrystals.

A well established method to minimize this problem is the operation ofthe electro-optical switching elements at an optical retardation set toa value considerably lower than that obtained as the theoreticallyoptimized value, e.g. the one optimised for maximum contrast. This wayof operation, however, has the significant drawback of reducing themaximum transmittance. The latter effect, however, is rather undesirablefor almost all kinds of electro-optical displays and in particular formobile displays.

Obviously, the phase range of the liquid-crystal mixture must besufficiently broad for the intended application of the display.

The response times of the liquid-crystal media in the displays also haveto be improved, i.e. reduced. This is particularly important fordisplays for television or multimedia applications. In order to improvethe response times, it has repeatedly been proposed in the past tooptimise the rotational viscosity of the liquid-crystal media (γ₁), i.e.to achieve media having the lowest possible rotational viscosity.However, the results achieved here are inadequate for many applicationsand therefore make it appear desirable to find further optimisationapproaches.

Adequate stability of the media to extreme loads, in particular to UVexposure and heating, is very particularly important. In particular inthe case of applications in displays in mobile equipment, such as, forexample, mobile telephones, this may be crucial.

The disadvantage of the MLC displays disclosed hitherto is due to theircomparatively low contrast, the relatively high viewing-angle dependenceand the difficulty in the reproduction of grey scales in these displays,especially when observed from an oblique viewing angle, as well as theirinadequate VHR and their inadequate lifetime.

There thus continues to be a great demand for MLC displays having veryhigh specific resistance at the same time as a large working-temperaturerange, short response times and a low threshold voltage, with the aid ofwhich various grey shades can be produced and which have, in particular,a good and stable VHR.

The invention has the object of providing MLC displays, not only formonitor and TV applications, but also for mobile applications such ase.g. telephones and navigation systems, which are based on the ECB, IPSor FFS effect, do not have the disadvantages indicated above, or only doso to a lesser extent, and at the same time have very high specificresistance values. In particular, it must be ensured for mobiletelephones and navigation systems that they also work at extremely highand extremely low temperatures.

Surprisingly, it has been found that it is possible to achieveliquid-crystal displays which have, in particular in ECB, IPS and FFSdisplays, a low threshold voltage with short response times and at thesame time a sufficiently broad nematic phase, favourable, relatively lowbirefringence (An) and, at the same time, a low birefringence dispersion(Δ(Δn)), good stability to decomposition by heating and by UV exposure,and a stable, high VHR if use is made in these display elements ofnematic liquid-crystal mixtures which comprise at least one compound,preferably two or more compounds, of formula I and in each case at leastone compound, preferably two or more compounds, of formula II,preferably selected from the group of the compounds of the sub-formulaeII-1 and II-2, particularly preferably the sub-formulate II-1 and/orII-2, and preferably additionally at least one compound, preferably twoor more compounds, selected from the group of the compounds of theformulae III-1 and III-2, preferably of formula III-2, and/or at leastone compound, preferably two or more compounds, of the formulae IVand/or V (all formulae as defined herein below).

Media of this type can be used, in particular, for electro-opticaldisplays having active-matrix addressing based on the ECB effect and forIPS (in-plane switching)—or FFS (fringe field switching) displays.

The invention thus relates to a liquid-crystalline medium based on amixture of polar compounds which comprises at least one compound offormula I and one or more compounds selected from the group of compoundsof formulae II and III, preferably one or more compounds of formula II,more preferably in addition one or more compounds of formula III and,most preferably additionally one or more compounds selected from thegroup of the compounds of formulae IV and V.

The mixtures according to the invention exhibit very broad nematic phaseranges with clearing points ≧70° C., very favourable values for thecapacitive threshold, relatively high values for the holding ratio andat the same time good low-temperature stabilities at −20° C. and −30°C., as well as very low rotational viscosities. The mixtures accordingto the invention are furthermore distinguished by a good ratio ofclearing point and rotational viscosity and by a high negativedielectric anisotropy.

Surprisingly, it has now been found that it is possible to achieveliquid-crystalline media having a suitably high absolute value of Δ∈(|Δ∈|), a suitable phase range and Δn with a low dispersion of thebirefringence, which do not have the disadvantages of the prior-artmaterials, or at least only do so to a considerably reduced extent.

Surprisingly, it has been found here that the compounds of formula I, asdefined herein below, when used, result in considerable, in many casesadequate, dispersion. This is the case, in particular, in most cases inwhich the parameter R¹¹ in the compounds of formula I used denotes alkylwith 1 to 5, preferably 1 to 3, C atoms. The compounds of formula I inwhich R¹¹ denotes alkyl with 1 to 3 C atoms and R¹² denotes H or methylare particularly preferably used.

The invention thus relates to compounds of formula I, and to aliquid-crystalline medium having a nematic phase and negative dielectricanisotropy, which comprises

-   a) one or more compounds of formula I, preferably in a concentration    in the range from 1% to 60%, more preferably in the range from 5% to    40%, particularly preferably in the range from 8% to 35%,

-   -   in which    -   a, b and c independently of each other denote an integer of 0 or        1,    -   c most preferably denotes 1,    -   (a+b+c) is 1, 2 or 3, preferably 1 or 2, most preferably 1,    -   R¹¹ and R¹² independently of each other denote H or alkyl with 1        to 7 C atoms, preferably H or alkyl with 1 to 53 C atoms, more        preferably H or alkyl with 1 to 3 C atoms, and, most preferably,    -   R¹¹ denotes H, methyl or ethyl, and    -   R¹² denotes H, methyl, ethyl or propyl, and

-   b) one or more compounds selected from the group of formulae II and    III

-   -   in which    -   R²¹ denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, preferably a straight-chain alkyl radical, more        preferably an n-alkyl radical, most preferably propyl or pentyl,        an unsubstituted alkenyl radical having 2 to 7 C atoms,        preferably a straight-chain alkenyl radical, particularly        preferably having 2 to 5 C atoms, an unsubstituted alkoxy        radical having 1 to 6 C atoms or an unsubstituted alkenyloxy        radical having 2 to 6 C atoms,    -   R²² denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, an unsubstituted alkoxy radical having 1 to 6 C atoms or        an unsubstituted alkenyloxy radical having 2 to 6 C atoms, and    -   I denotes 0 or 1,

-   -   in which    -   R³¹ denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, preferably a straight-chain alkyl radical, more        preferably an n-alkyl radical, most preferably propyl or pentyl,        or an unsubstituted alkenyl radical having 2 to 7 C atoms,        preferably a straight-chain alkenyl radical, particularly        preferably having 2 to 5 C atoms,    -   R³² denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, preferably having 2 to 5 C atoms, an unsubstituted alkoxy        radical having 1 to 6 C atoms, preferably having 1, 2, 3 or 4 C        atoms, or an unsubstituted alkenyloxy radical having 2 to 6 C        atoms, preferably having 2, 3 or 4 C atoms, and

denotes

and

-   c) optionally, preferably obligatorily, one or more compounds of    formula IV,

in which

-   R⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms or    an unsubstituted alkenyl radical having 2 to 7 C atoms, both    preferably having 2 to 5 C atoms, preferably having 2, 3 or 4 C    atoms, more preferably a vinyl radical or a 1-propenyl radical and    in particular a vinyl radical, and-   R⁴² denotes an unsubstituted alkyl radical having 1 to 7 C atoms or    an unsubstituted alkoxy radical having 1 to 6 C atoms, preferably an    n-alkyl radical, particularly preferably having 2, 3, 4 or 5 C    atoms,-   d) optionally, preferably obligatorily, one or more compounds of    formula V,

-   in which-   R⁵¹ and R⁵², independently of one another, have one of the meanings    given for R²¹ and R²² and preferably denote alkyl having 1 to 7 C    atoms, preferably n-alkyl, particularly preferably n-alkyl having 1    to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy,    particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl,    alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to    4 C atoms, preferably alkenyloxy,

to

if present, each, independently of one another, denote

preferably

preferably

denotes

and, if present,

preferably denotes

-   Z⁵¹ to Z⁵³ each, independently of one another, denote —CH₂—CH₂—,    —CH₂—O—, —CH═CH—, —C≡C—, —COO— or a single bond, preferably    —CH₂—CH₂—, —CH₂—O— or a single bond and particularly preferably a    single bond,-   i and j each, independently of one another, denote 0 or 1,-   (i+j) preferably denotes 0 or 1.

In the present application, the elements all include their respectiveisotopes. In particular, one or more H in the compounds may be replacedby D, and this is also particularly preferred in some embodiments. Acorrespondingly high degree of deuteration of the correspondingcompounds enables, for example, detection and recognition of thecompounds. This is very helpful in some cases, in particular in the caseof the compounds of formula I.

In the present application,

-   alkyl particularly preferably denotes straight-chain alkyl, in    particular CH₃—, C₂H₅—, n-C₃H₇—, n-C₄H₉— or n-C₅H₁₁—, and-   alkenyl particularly preferably denotes CH₂═CH—, E-CH₃—CH═CH—,    CH₂═CH—CH₂—CH₂—, E-CH₃—CH═CH—CH₂—CH₂— or E-(n-C₃H₇)—CH═CH—.

Preferably the liquid crystalline media according to the presentinvention comprise one or more compounds of formula I selected from thefollowing group of compounds of formulae I-1 to I-3, preferably selectedfrom formulae I-1 and I-2, most preferably of formula I-1

wherein the parameters have the respective meanings, including the samepreferred meanings, given above under formula I, andin formula I-1

-   -   R¹¹ preferably denotes methyl, ethyl, propyl, butyl or pentyl,        more preferably n-propyl, n-butyl or n-pentyl),    -   R¹² preferably denotes H, methyl or ethyl,        in formula I-2    -   R¹¹ preferably denotes methyl, ethyl, propyl, butyl or pentyl,        more preferably n-propyl, n-butyl or n-pentyl,    -   R¹² preferably denotes H or methyl,        in formula I-3    -   R¹¹ preferably denotes H, methyl of ethyl, more preferably H or        methyl, most preferably H, and    -   R¹² preferably denotes H or methyl, more preferably H.

Preferably the liquid crystalline media according to the presentinvention comprise one or more compounds of formula I-1 selected fromthe following group of compounds of formulae I-1a to I-1, preferablyselected from formulae I-1a and I-1b, most preferably of formula I-1b

Preferably the liquid crystalline media according to the presentinvention comprise alternatively or additionally to the compounds offormulae I-1 and/or I-3 one or more compounds of formula I-2 selectedfrom the following group of compounds of formulae I-2a to I-2h,preferably selected from formulae I-2c and I-2d, most preferably offormula I-2c.

Preferably the liquid crystalline media according to the presentinvention alternatively or additionally to the compounds of formula I-1and/or I-2 comprise one or more compounds of formula I selected from thefollowing group of compounds of formulae I-3a to I-3f, preferablyselected from formulae I-3a, I-3b, I-3c and I-3f, most preferably offormula I-3a, I-3b and I1-3c.

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaI selected from the group of the compounds of the formulae I-1 to I-3,preferably selected from the group of the compounds of the formulae (I-1and I-2) or (I-1 and I-3).

In an even more preferred embodiment of the present invention, the mediaaccording to the invention in each case comprise one or more compoundsof formula I selected from the group of the following compounds of theformulae I-1a to I-1d.

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaI selected from the group of the following compounds of the formulaeI-1b.

In an alternative, preferred embodiment of the present invention, themedia according to the invention in each case comprise one or morecompounds of formula I selected from the group of the followingcompounds of the formulae I-1f and I-1g.

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaII selected from the group of the compounds of the formulae II-1 andII-2, preferably one or more compounds each of formulae II-1 and one ormore compounds of formula II-2,

-   -   in which the parameters have the respective meanings given above        under formula II, and preferably    -   in formula II-1    -   R²¹ and R²² independently of each other denote methoxy, ethoxy,        propoxy, butoxy (also or pentoxy, preferably ethoxy, butoxy or        pentoxy, more preferably ethoxy or butoxy and, most preferably        butoxy.    -   in formula II-2    -   R²¹ preferably denotes vinyl, 1-E-propenyl, but-4-en-1-yl,        pent-1-en-1-yl or pent-3-en-1-yl and n-propyl or n-pentyl and    -   R²² denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, preferably having 2 to 5 C atoms, or, preferably, an        unsubstituted alkoxy radical having 1 to 6 C atoms, particularly        preferably having 2 or 4 C atoms and, most preferably, ethoxy,        and

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaIII selected from the group of the compounds of the formulae III-1 andIII-2, preferably one or more compounds each of the formulae III-1 andone or more compounds of formula III-2,

-   -   in which the parameters have the respective meanings given above        underformula III, and preferably    -   R³¹ denotes vinyl, 1-E-propenyl, but-4-en-1-yl, pent-1-en-1-yl        or pent-3-en-1-yl, n-propyl or n-pentyl and    -   R³² denotes an unsubstituted alkyl radical having 1 to 7 C        atoms, preferably having 2 to 5 C atoms, or, preferably, an        unsubstituted alkoxy radical having 1 to 6 C atoms, particularly        preferably having 2 or 4 C atoms and, most preferably, ethoxy.

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaII-1 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaII-2 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media accordingIn a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaIII-1 selected from the group of the following compounds:

In a preferred embodiment of the present invention, the media accordingto the invention in each case comprise one or more compounds of formulaIII-2 selected from the group of the following compounds:

In addition to the compounds of formula I or the preferred sub-formulaethereof, the media in accordance with the present invention preferablycomprise one or more dielectrically neutral compounds selected from thegroup of compounds of the formulae II and III preferably in a totalconcentration in the range from 5% or more to 90% or less, preferablyfrom 10% or more to 80% or less, particularly preferably from 20% ormore to 70% or less.

In a further preferred embodiment, the medium comprises one or morecompounds of formula IV

one or more compounds of formula IV

in which

-   R⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms or    an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably    an n-alkyl radical, particularly preferably having 2, 3, 4 or 5 C    atoms, and-   R⁴² denotes an unsubstituted alkyl radical having 1 to 7 C atoms or    an unsubstituted alkoxy radical having 1 to 6 C atoms, both    preferably having 2 to 5 C atoms, an unsubstituted alkenyl radical    having 2 to 7 C atoms, preferably having 2, 3 or 4 C atoms, more    preferably a vinyl radical or 1-propenyl radical and in particular a    vinyl radical.

In a particularly preferred embodiment, the medium comprises one or morecompounds of formula IV selected from the group of the compounds of theformulae IV-1 to IV-3, preferably of formula IV-1,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having    1 to 7 C atoms, preferably having 2 to 5 C atoms,-   alkenyl denotes an alkenyl radical having 2 to 5 C atoms, preferably    having 2 to 4 C atoms, particularly preferably 2 C atoms,-   alkenyl′ denotes an alkenyl radical having 2 to 5 C atoms,    preferably having 2 to 4 C atoms, particularly preferably having 2    to 3 C atoms, and-   alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to    4 C atoms.

In a particularly preferred embodiment, the media according to theinvention comprise one or more compounds of formula IV-1 and/or one ormore compounds of formula IV-2.

In a further preferred embodiment, the medium comprises one or morecompounds of formula V

in which

-   R⁵¹ and R⁵², independently of one another, have one of the meanings    given for R²¹ and R²² and preferably denote alkyl having 1 to 7 C    atoms, preferably n-alkyl, particularly preferably n-alkyl having 1    to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy,    particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl,    alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to    4 C atoms, preferably alkenyloxy,

to

-   -   if present, each, independently of one another, denote

preferably

preferably

denotes

and, if present,

preferably denotes

-   Z⁵¹ to Z⁵³ each, independently of one another, denote —CH₂—CH₂—,    —CH₂—O—, —CH═CH—, —C≡C—, —COO— or a single bond, preferably    —CH₂—CH₂—, —CH₂—O— or a single bond and particularly preferably a    single bond,-   i and j each, independently of one another, denote 0 or 1,-   (i+j) preferably denotes 0, 1 or 2, more preferably 0 or 1 and, most    preferably, 1.

The media according to the invention preferably comprise the followingcompounds in the total concentrations indicated:

-   -   1-60% by weight of one or more compounds selected from the group        of the compounds of formula I and    -   5-60% by weight of one or more compounds of formula II,        preferably selected from the group of the compounds of the        formulae II-1 and II-2 and/or    -   10-60% by weight of one or more compounds of formula III,        preferably selected from the group of the compounds of the        formulae III-1 and III-2 and/or    -   0-60% by weight of one or more compounds of the formulae IV        and/or V,    -   where the total content of all compounds in the medium        preferably is 95% or more and, more preferably 100%.

In a further preferred embodiment, the media in accordance with thepresent invention in addition to the compounds of formula I or thepreferred sub-formulae thereof, and to the compounds of formulae IIand/or III, preferably comprise one or more dielectrically neutralcompounds selected from the group of compounds of formulae IV and Vpreferably in a total concentration in the range from 5% or more to 90%or less, preferably from 10% or more to 80% or less, particularlypreferably from 20% or more to 70% or less.

The medium according to the invention in a particularly preferredembodiment comprises

-   -   one or more compounds of formula II in a total concentration in        the range from 5% or more to 50% or less, preferably in the        range from 10% or more to 40% or less, and/or    -   one or more compounds of formula III-1 in a total concentration        in the range from 5% or more to 30% or less, and/or    -   one or more compounds of formula III-2 in a total concentration        in the range from 3% or more to 30% or less.

Preferably the concentration of the compounds of formula I in the mediaaccording to the invention is in the range from 1% or more to 60% orless, more preferably from 5% or more to 40% or less, most preferablyfrom 8% or more to 35% or less

In a preferred embodiment of the present invention the concentration ofthe compounds of formula II in the media is in the range from 3% or moreto 60% or less, more preferably from 5% or more to 55% or less, morepreferably from 10% or more to 50% or less and, most preferably, from15% or more to 45% or less.

In a preferred embodiment of the present invention the concentration ofthe compounds of formula III in the media is in the range from 2% ormore to 50% or less, more preferably from 5% or more to 40% or less,more preferably from 10% or more to 35% or less and, most preferably,from 15% or more to 30% or less.

In a preferred embodiment of the present invention the concentration ofthe compounds of formula III-1 in the media is in the range from 1% ormore to 40% or less, more preferably either from 2% or more to 35% orless, or, alternatively, from 15% or more to 25% or less.

In a preferred embodiment of the present invention the concentration ofthe compounds of formula III-2 in the media, if present, is in the rangefrom 1% or more to 40% or less, more preferably from 5% or more to 35%or less and, most preferably, from 10% or more to 30% or less.

The present invention also relates to electro-optical displays orelectro-optical components which contain liquid-crystalline mediaaccording to the invention. Preference is given to electro-opticaldisplays which are based on the VA, ECB, IPS or FFS effect, preferablyon the VA; IPS or FFS effect, and in particular those which areaddressed by means of an active-matrix addressing device.

Accordingly, the present invention likewise relates to the use of aliquid-crystalline medium according to the invention in anelectro-optical display or in an electro-optical component, and to aprocess for the preparation of the liquid-crystalline media according tothe invention, characterised in that one or more compounds of formula Iare mixed with one or more compounds of formula II, preferably with oneor more compounds of the sub-formulae II-1 and/or II-2 and/or with oneor more compounds of formula III, preferably with one or more compoundsof the sub-formulae III-1 and/or III-2, particularly preferably one ormore compounds from two or more, preferably from three or more,different formulae thereof and very particularly preferably from allfour of these formulae II-1, II-2, III-1 and III-2 and one or morefurther compounds, preferably selected from the group of the compoundsof the formulae IV and V, more preferably with one or more compoundsboth of formula IV and of formula V.

In a further preferred embodiment, the medium comprises one or morecompounds of formula IV, selected from the group of the compounds of theformulae IV-2 and IV-3,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having    1 to 7 C atoms, preferably having 2 to 5 C atoms,-   alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to    4 C atoms.

In a further preferred embodiment, the medium comprises one or morecompounds of formula V selected from the group of the compounds of theformulae V-1 and V-2, preferably of formulae V-1,

in which the parameters have the meanings given above under formula V,and preferably

-   R⁵¹ denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C    atoms, and-   R⁵² denotes alkyl having 1 to 7 C atoms, alkenyl having 2 to 7 C    atoms or alkoxy having 1 to 6 C atoms, preferably alkyl or alkenyl,    particularly preferably alkyl.

In a further preferred embodiment, the medium comprises one or morecompounds of formula V-1 selected from the group of the compounds of theformulae V-1a and V-1b,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having    1 to 7 C atoms, preferably having 2 to 5 C atoms, and-   alkenyl denotes alkenyl having 2 to 7 C atoms, preferably having 2    to 5 C atoms.

In addition, the present invention relates to a method for the reductionof the wavelength dispersion of the birefringence of aliquid-crystalline medium which comprises one or more compounds offormula II, optionally one or more compounds selected from the group ofthe compounds of the formulae III-1 and III-2 and/or one or morecompounds of formula IV and/or one or more compounds of formula V,characterised in that one or more compounds of formula I are used in themedium.

Besides compounds of the formulae I to V, other constituents may also bepresent, for example in an amount of up to 45%, but preferably up to35%, in particular up to 10%, of the mixture as a whole.

The media according to the invention may optionally also comprise adielectrically positive component, whose total concentration ispreferably 20% or less, more preferably 10% or less, based on the entiremedium.

In a preferred embodiment, the liquid-crystal media according to theinvention comprise in total, based on the mixture as a whole,

20% or more to 60% or less, preferably 25% or more to 50% or less,particularly preferably 30% or more to 45% or less, of the compound offormula I,20% or more to 60% or less, preferably 25% or more to 50% or less,particularly preferably 30% or more to 45% or less, of compounds offormula II, and50% or more to 70% or less of compounds of the formulae III-1 and III-2.

The liquid-crystal media in accordance with the present invention maycomprise one or more chiral compounds.

Particularly preferred embodiments of the present invention meet one ormore of the following conditions,

where the acronyms (abbreviations) are explained in Tables A to C andillustrated by examples in Table D.

Preferably the media according to the present invention fulfil one ormore of the following conditions.

-   i. The liquid-crystalline medium has a birefringence of 0.060 or    more, particularly preferably 0.070 or more.-   ii. The liquid-crystalline medium has a birefringence of 0.130 or    less, particularly preferably 0.120 or less.-   iii. The liquid-crystalline medium has a birefringence in the range    from 0.090 or more to 0.120 or less.-   iv. The liquid-crystalline medium has a negative dielectric    anisotropy having an absolute value of 2.0 or more, particularly    preferably 3.0 or more and, most preferably of 3.5 or more.-   v. The liquid-crystalline medium has a negative dielectric    anisotropy having an absolute value of 5.5 or less, particularly    preferably 4.0 or less.-   vi. The liquid-crystalline medium has a negative dielectric    anisotropy having an absolute value in the range from 2.5 or more to    4.5 or less, preferably from 3.0 or more to 4.0 or less.-   vii. The liquid-crystalline medium comprises one or more    particularly preferred compounds of formula I-1 selected from the    sub-formulae given below:

-   -   in which alkyl has the meaning given above and preferably, in        each case independently of one another, denotes alkyl having 1        to 6, preferably having 2 to 5, C atoms and particularly        preferably n-alkyl.

-   viii. The liquid-crystalline medium comprises one or more    particularly preferred compounds of formula I-2 selected from the    sub-formulae given below:

-   -   in which alkyl has the meaning given above and preferably, in        each case independently of one another, denotes alkyl having 1        to 6, preferably having 2 to 5, C atoms and particularly        preferably n-alkyl.

-   ix. The liquid-crystalline medium comprises one or more particularly    preferred compounds of formula I-1 selected from the sub-formulae    given below:

-   x. The liquid-crystalline medium comprises one or more particularly    preferred compounds of formula IV selected from the sub-formulae    given below:

-   -   in which alkyl has the meaning given above and preferably, in        each case independently of one another, denotes alkyl having 1        to 6, preferably having 2 to 5, C atoms and particularly        preferably n-alkyl.

-   xi. The total concentration of the compounds of formula II in the    mixture as a whole is 25% or more, preferably 30% or more, and is    preferably in the range from 25% or more to 49% or less,    particularly preferably in the range from 29% or more to 47% or    less, and very particularly preferably in the range from 37% or more    to 44% or less.

-   xii. The liquid-crystalline medium comprises one or more compounds    of formula II selected from the group of the compounds of the    following formulae: CC-n-V and/or CC-n-Vm, particularly preferably    CC-3-V, preferably in a concentration of up to 50% or less,    particularly preferably up to 42% or less, and optionally    additionally CC-3-V1, preferably in a concentration of up to 15% or    less, and/or CC-4-V, preferably in a concentration of up to 20% or    less, particularly preferably up to 10% or less.

-   xiii. The total concentration of the compounds selected from the    group of formulae CC-3-VV, CC-3-VV1, CVC-3-V, CC-V-V, CC-V-V1,    CC-1V-V1 and CC-2V-V2 in the mixture as a whole is 5% or more,    preferably 10% or more, preferably 15% or more, more preferably 20%    or more and, most preferably, 25% or more.

-   xiv. The media comprise one or more compounds selected from the    group of compounds of formulae CC-3-VV, CC-3-VV1 and CVC-3-V.

-   xv. The media comprise the compound of formula CC-3-VV, preferably    in a concentration of 5% or more to 60% or less, more preferably in    a concentration of 6% or more to 35% or less.

-   xvi. The media comprise the compound of formula CVC-3-V, preferably    in a concentration of 5% or more to 40% or less, more preferably in    a concentration of 6% or more to 30% or less.

-   xvii. The total concentration of the compounds selected from the    group of formulae CC-3-VV, CC-3-VV1, CVC-3-V, CC-V-V, CC-V-V1,    CC-1V-V1 and CC-2V-V2 in the mixture as a whole is 10% or more,    preferably 15% or more, more preferably 20% or more and, most    preferably, 25% or more.

-   xviii. The media comprise the compound of formula CC-V-V, preferably    in a concentration of 5% or more to 60% or less, more preferably in    a concentration of 10% or more to 25% or less.

-   xix. The media comprise the compound of formula CC-V-V1, preferably    in a concentration of 5% or more to 60% or less, more preferably in    a concentration of 10% or more to 25% or less.

-   xx. The media comprise the compound of formula CC-1V-V1, preferably    in a concentration of 5% or more to 35% or less, more preferably in    a concentration of 10% or more to 25% or less.

-   xxi. The media comprise the compound of formula CC-2V-V2, preferably    in a concentration of 5% or more to 35% or less, more preferably in    a concentration of 5% or more to 15% or less.

-   xxii. The media comprise the compound of formula CC-n-V, preferably    CC-3-V, preferably in a concentration of 1% or more to 60% or less,    more preferably in a concentration of 3% or more to 35% or less.

-   xxiii. The total concentration of the compounds of formula CC-3-V in    the mixture as a whole preferably either is 15% or less, preferably    10% or less or 20% or more, preferably 25% or more.

-   xxiv. The total concentration of the compounds of formula Y-nO-Om in    the mixture as a whole is 2% or more to 30% or less, preferably 5%    or more to 15% or less.

-   xxv. The total concentration of the compounds of formula CY-n-Om in    the mixture as a whole is 5% or more to 60% or less, preferably 15%    or more to 45% or less.

-   xxvi. The total concentration of the compounds of formula CCY-n-Om    and/or CCY-n-m, preferably of CCY-n-Om, in the mixture as a whole is    5% or more to 40% or less, preferably 1% or more to 25% or less.

-   xxvii. The total concentration of the compounds of formula CLY-n-Om    in the mixture as a whole is 5% or more to 40% or less, preferably    10% or more to 30% or less.

-   xxviii. The liquid-crystalline medium essentially consists of    compounds of the formulae I, II-1, II-2, III-1, III-2, IV and V,    preferably of compounds of the formulae I, II-1, II-2, III-1 and    III-2.

-   xxix. The liquid-crystalline medium comprises one or more compounds    of formula IV, preferably of the formulae IV-1 and/or IV-2,    preferably in a total concentration of 1% or more, in particular 2%    or more, and very particularly preferably 3% or more to 50% or less,    preferably 35% or less.

-   xxx. The liquid-crystalline medium comprises one or more compounds    of formula V, preferably of the formulae V-1 and/or V-2, preferably    in a total concentration of 1% or more, in particular 2% or more,    and very particularly preferably 15% or more to 35% or less,    preferably to 30% or less.

-   xxxi. The total concentration of the compounds of formula CCP-V-n,    preferably CCP-V-1, in the mixture as a whole preferably is 5% or    more to 30% or less, preferably 15% or more to 25% or less.

-   xxxii. The total concentration of the compounds of formula CCP-V2-n,    preferably CCP-V2-1, in the mixture as a whole preferably is 1% or    more to 15% or less, preferably 2% or more to 10% or less.

The invention furthermore relates to an electro-optical display havingactive-matrix addressing based on the VA, ECB, IPS, FFS or UB-FFSeffect, characterised in that it contains, as dielectric, aliquid-crystalline medium in accordance with the present invention.

The liquid-crystal mixture preferably has a nematic phase range having awidth of at least 70 degrees.

The liquid-crystal mixture according to the invention has a Δ∈ of −0.5to −8.0, in particular −1.5 to −6.0, and very particularly preferably−2.0 to −5.0, where Δ∈ denotes the dielectric anisotropy.

The rotational viscosity γ₁ is preferably 120 mPa·s or less, inparticular 100 mPa·s or less.

The mixtures according to the invention are suitable for all VA-TFTapplications, such as, for example, VAN, MVA, (S)-PVA, ASV, PAVA andPSVA. They are furthermore suitable for IPS (in-plane switching), FFS(fringe-field switching) and PALC applications having negative Δ∈.

The nematic liquid-crystal mixtures in the displays according to theinvention generally comprise two components A and B, which themselvesconsist of one or more individual compounds.

The liquid-crystalline media according to the invention preferablycomprise 4 to 15, in particular 5 to 12, and particularly preferably 10or less, compounds. These are preferably selected from the group of thecompounds of the formulae I, II-1, II-2, III-1 and III-2 and/or IVand/or V.

The liquid-crystalline media according to the invention may optionallyalso comprise more than 18 compounds. In this case, they preferablycomprise 18 to 25 compounds.

In a preferred embodiment, the liquid-crystal media according to theinvention comprise compounds selected from the group of the compounds ofthe formulae I, II, III, IV and V, preferably selected from the group ofthe compounds of the formulae I, II, III-1 and III-2; they preferablyconsist predominantly, particularly preferably essentially and veryparticularly preferably virtually completely of the compounds of thesaid formulae.

The liquid-crystal media according to the invention preferably have anematic phase from in each case at least −20° C. or less to 70° C. ormore, particularly preferably from −30° C. or less to 80° C. or more,very particularly preferably from −40° C. or less to 85° C. or more andmost preferably from −40° C. or less to 90° C. or more.

The expression “have a nematic phase” here means on the one hand that nosmectic phase and no crystallisation are observed at low temperatures atthe corresponding temperature and on the other hand that no clearingoccurs on heating out of the nematic phase. The investigation at lowtemperatures is carried out in a flow viscometer at the correspondingtemperature and checked by storage in test cells having a cell thicknesscorresponding to the electro-optical application for at least 100 hours.If the storage stability at a temperature of −20° C. in a correspondingtest cell is 1000 h or more, the medium is regarded as stable at thistemperature. At temperatures of −30° C. and −40° C., the correspondingtimes are 500 h and 250 h respectively. At high temperatures, theclearing point is measured in capillaries by conventional methods.

In a preferred embodiment, the liquid-crystal media according to theinvention are characterised by optical anisotropy values in the moderateto low range. The birefringence values are preferably in the range from0.065 or more to 0.130 or less, particularly preferably in the rangefrom 0.080 or more to 0.120 or less and very particularly preferably inthe range from 0.085 or more to 0.110 or less.

In this embodiment, the liquid-crystal media according to the inventionhave negative dielectric anisotropy and relatively high absolute valuesof the dielectric anisotropy (|Δ∈|) which are preferably in the rangefrom 2.7 or more to 5.3 or less, preferably to 4.5 or less, preferablyfrom 2.9 or more to 4.5 or less, particularly preferably from 3.0 ormore to 4.0 or less and very particularly preferably from 3.5 or more to3.9 or less.

The liquid-crystal media according to the invention have relatively lowvalues for the threshold voltage (V₀) in the range from 1.7 V or more to2.5 V or less, preferably from 1.8 V or more to 2.4 V or less,particularly preferably from 1.9 V or more to 2.35 V or less.

In a further preferred embodiment, the liquid-crystal media according tothe invention preferably have relatively low values of the averagedielectric anisotropy (∈_(av.)≡(∈_(∥)+2∈_(⊥))/3) which are preferably inthe range from 5.0 or more to 7.2 or less, preferably from 5.5 or moreto 6.9 or less, still more preferably from 6.0 or more to 6.7 or less,particularly preferably from 5.6 or more to 6.1 or less and veryparticularly preferably from 6.1 or more to 6.5 or less.

In addition, the liquid-crystal media according to the invention havehigh values for the VHR in liquid-crystal cells.

In freshly filled cells at 20° C. in the cells, these are greater thanor equal to 95%, preferably greater than or equal to 97%, particularlypreferably greater than or equal to 98% and very particularly preferablygreater than or equal to 99%, and after 5 minutes in the oven at 100° C.in the cells, these are greater than or equal to 90%, preferably greaterthan or equal to 93%, particularly preferably greater than or equal to96% and very particularly preferably greater than or equal to 98%.

In general, liquid-crystal media having a low addressing voltage orthreshold voltage here have a lower VHR than those having a higheraddressing voltage or threshold voltage, and vice versa.

These preferred values for the individual physical properties arepreferably also in each case maintained by the media according to theinvention in combination with one another.

In the present application, the term “compounds”, also written as“compound(s)”, means both one and also a plurality of compounds, unlessexplicitly indicated otherwise.

In a preferred embodiment, the liquid-crystalline media according to theinvention comprise

one or more compounds of formula I,one or more compounds of formula II, preferably of the formulae Y-nO-Omand/or CY-n-Om, selected from the group of the compounds of the formulaeY-4O-O4, CY-3-O2, CY-3-O4, CY-5-O2 and CY-5-O4,optionally, preferably obligatorily, one or more compounds of formulaIII-1, preferably selected from the group of the compounds of theformulae CCY-n-m and CCY-n-Om, preferably of formula CCY-n-Om,preferably selected from the group of the compounds of the formulaeCCY-3-O2, CCY-2-O2, CCY-3-O1, CCY-3-O3, CCY-4-O2, CCY-3-O2 and CCY-5-O2,optionally, preferably obligatorily, one or more compounds of formulaIII-2, preferably of formula CLY-n-Om, preferably selected from thegroup of the compounds of the formulae CLY-2-O4, CLY-3-O2, CLY-3-O3,optionally, preferably obligatorily, one or more compounds of formulaIV, preferably selected from the group of the compounds of the formulaeCC-n-V and CC-n-Vm, preferably CC-3-V, CC-3-V1, CC-4-V and CC-5-V,particularly preferably selected from the group of the compounds CC-3-V,CC-3-V1 and CC-4-V, very particularly preferably the compound CC-3-V,and optionally additionally the compound(s) CC-4-V and/or CC-3-V1, andoptionally, preferably obligatorily, one or more compounds of formula V,preferably of the formulae CCP-V-1 and/or CCP-V2-1.

In a specific preferred embodiment of the present invention, the mediaaccording to the invention comprise one or more compounds of formula VI,

in which

-   R⁶¹ and R⁶² independently of one another have the meaning given for    R³² above,-   R⁶¹ preferably denotes an alkyl radical having 2 to 5 C atoms,    preferably having 3 to 5 C atoms,-   R⁶² preferably denotes an alkyl or alkoxy radical having 2 to 5 C    atoms, more preferably an alkoxy radical having 2 to 4 C atoms, or    an alkenyloxy radical having 2 to 4 C atoms.

denotes

-   p and q independently of each other denote 0 or 1, and-   (p+q) preferably denotes 0 or 1.

These compounds are highly suitable as stabilisers in liquid-crystalmixtures, especially in case p=q=1 and ring A⁶=1,4-phenylenbe. Inparticular, they stabilise the VHR of the mixtures against UV exposure.

In a preferred embodiment the media according to the invention compriseone or more compounds of formula VI selected from one or more formulaeof the group of the compounds of the formulae VI-1 to VI-4, veryparticularly preferably of the formulae VI-1 to VI-3,

in which the parameters have the meanings given under formula VI.

In a further preferred embodiment, the medium comprises one or morecompounds of formula VI-3, preferably of formula VI-3-a,

in which

-   alkyl and alkyl′, independently of one another, denote alkyl having    1 to 7 C atoms, preferably having 2 to 5 C atoms.

In case the compounds of formula VI are used in the liquid crystallinemedia according to the present application, they are preferably presentin a concentration of 20% or less, more preferably of 10% or less and,most preferably, of 5% or less and for the individual i.e. (homologous)compounds preferably in a concentration of 10% or less and, morepreferably, of 5% or less.

For the present invention, the following definitions apply in connectionwith the specification of the constituents of the compositions, unlessindicated otherwise in individual cases:

-   -   “comprise”: the concentration of the constituents in question in        the composition is preferably 5% or more, particularly        preferably 10% or more, very particularly preferably 20% or        more,    -   “predominantly consist of”: the concentration of the        constituents in question in the composition is preferably 50% or        more, particularly preferably 55% or more and very particularly        preferably 60% or more,    -   “essentially consist of”: the concentration of the constituents        in question in the composition is preferably 80% or more,        particularly preferably 90% or more and very particularly        preferably 95% or more, and    -   “virtually completely consist of”: the concentration of the        constituents in question in the composition is preferably 98% or        more, particularly preferably 99% or more and very particularly        preferably 100.0%.

This applies both to the media as compositions with their constituents,which can be components and compounds, and also to the components withtheir constituents, the compounds. Only in relation to the concentrationof an individual compound relative to the medium as a whole does theterm comprise mean: the concentration of the compound in question ispreferably 1% or more, particularly preferably 2% or more, veryparticularly preferably 4% or more.

For the present invention, “≦” means less than or equal to, preferablyless than, and “≧” means greater than or equal to, preferably greaterthan.

For the present invention,

denote trans-1,4-cyclohexylene, and

denote 1,4-phenylene.

For the present invention, the expression “dielectrically positivecompounds” means compounds having a Δ∈ of >1.5, the expression“dielectrically neutral compounds” means those where −1.5≦Δ∈≦1.5 and theexpression “dielectrically negative compounds” means those whereΔ∈<−1.5. The dielectric anisotropy of the compounds is determined hereby dissolving 10% of the compounds in a liquid-crystalline host anddetermining the capacitance of the resultant mixture in each case in atleast one test cell having a cell thickness of 20 μm with homeotropicand with homogeneous surface alignment at 1 kHz. The measurement voltageis typically 0.5 V to 1.0 V, but is always lower than the capacitivethreshold of the respective liquid-crystal mixture investigated.

The host mixture used for dielectrically positive and dielectricallyneutral compounds is ZLI-4792 and that used for dielectrically negativecompounds is ZLI-2857, both from Merck KGaA, Germany. The values for therespective compounds to be investigated are obtained from the change inthe dielectric constant of the host mixture after addition of thecompound to be investigated and extrapolation to 100% of the compoundemployed. The compound to be investigated is dissolved in the hostmixture in an amount of 10%. If the solubility of the substance is toolow for this purpose, the concentration is halved in steps until theinvestigation can be carried out at the desired temperature.

The liquid-crystal media according to the invention may, if necessary,also comprise further additives, such as, for example, stabilisersand/or pleochroitic, e.g. dichroitic, dyes and/or chiral dopants in theusual amounts. The amount of these additives employed is preferably intotal 0% or more to 10% or less, based on the amount of the entiremixture, particularly preferably 0.1% or more to 6% or less. Theconcentration of the individual compounds employed is preferably 0.1% ormore to 3% or less. The concentration of these and similar additives isgenerally not taken into account when specifying the concentrations andconcentration ranges of the liquid-crystal compounds in theliquid-crystal media.

In a preferred embodiment, the liquid-crystal media according to theinvention comprise a polymer precursor which comprises one or morereactive compounds, preferably reactive mesogens, and, if necessary,also further additives, such as, for example, polymerisation initiatorsand/or polymerisation moderators, in the usual amounts. The amount ofthese additives employed is in total 0% or more to 10% or less, based onthe amount of the entire mixture, preferably 0.1% or more to 2% or less.The concentration of these and similar additives is not taken intoaccount when specifying the concentrations and concentration ranges ofthe liquid-crystal compounds in the liquid-crystal media.

The compositions consist of a plurality of compounds, preferably 3 ormore to 30 or fewer, particularly preferably 6 or more to 20 or fewerand very particularly preferably 10 or more to 16 or fewer compounds,which are mixed in a conventional manner. In general, the desired amountof the components used in lesser amount is dissolved in the componentsmaking up the principal constituent of the mixture. This isadvantageously carried out at elevated temperature. If the selectedtemperature is above the clearing point of the principal constituent,completion of the dissolution operation is particularly easy to observe.However, it is also possible to prepare the liquid-crystal mixtures inother conventional ways, for example using pre-mixes or from a so-called“multi-bottle system”.

The mixtures according to the invention exhibit very broad nematic phaseranges having clearing points of 65° C. or more, very favourable valuesfor the capacitive threshold, relatively high values for the holdingratio and at the same time very good low-temperature stabilities at −30°C. and −40° C. Furthermore, the mixtures according to the invention aredistinguished by low rotational viscosities γ₁.

It goes without saying to the person skilled in the art that the mediaaccording to the invention for use in VA, IPS, FFS or PALC displays mayalso comprise compounds in which, for example, H, N, O, Cl, F have beenreplaced by the corresponding isotopes.

The structure of the liquid-crystal displays according to the inventioncorresponds to the usual geometry, as described, for example, in EP-A 0240 379.

The liquid-crystal phases according to the invention can be modified bymeans of suitable additives in such a way that they can be employed inany type of, for example, ECB, VAN, IPS, GH(Guest-Host) or ASM (axiallysymmetric microdomaoin)—VA LCD display that has been disclosed to date.

Table E below indicates possible dopants which can be added to themixtures according to the invention. If the mixtures comprise one ormore dopants, it is (they are) employed in amounts of 0.01% to 4%,preferably 0.1% to 1.0%.

Stabilisers which can be added, for example, to the mixtures accordingto the invention, preferably in amounts of 0.01% to 6%, in particular0.1% to 3%, are shown below in Table F.

For the purposes of the present invention, all concentrations are,unless explicitly noted otherwise, indicated in percent by weight andrelate to the corresponding mixture or mixture component, unlessexplicitly indicated otherwise.

All temperature values indicated in the present application, such as,for example, the melting point T(C,N), the smectic (S) to nematic (N)phase transition T(S,N) and the clearing point T(N,I), are indicated indegrees Celsius (° C.) and all temperature differences arecorrespondingly indicated in differential degrees (° or degrees), unlessexplicitly indicated otherwise.

For the present invention, the term “threshold voltage” relates to thecapacitive threshold (V₀), also known as the Freedericks threshold,unless explicitly indicated otherwise.

All physical properties are and have been determined in accordance with“Merck Liquid Crystals, Physical Properties of Liquid Crystals”, statusNovember 1997, Merck KGaA, Germany, and apply for a temperature of 20°C., and Δn is determined at 436 nm, 589 nm and at 633 nm, and Δ∈ at 1kHz, unless explicitly indicated otherwise in each case.

The electro-optical properties, for example the threshold voltage (V₀)(capacitive measurement), are, as is the switching behaviour, determinedin test cells produced at Merck Japan. The measurement cells havesoda-lime glass substrates and are constructed in an ECB or VAconfiguration with polyimide alignment layers (SE-1211 with diluent **26(mixing ratio 1:1), both from Nissan Chemicals, Japan), which have beenrubbed perpendicularly to one another and effect homeotropic alignmentof the liquid crystals. The surface area of the transparent, virtuallysquare ITO electrodes is 1 cm².

Unless indicated otherwise, a chiral dopant is not added to theliquid-crystal mixtures used, but the latter are also particularlysuitable for applications in which doping of this type is necessary.

The rotational viscosity is determined using the rotating permanentmagnet method and the flow viscosity in a modified Ubbelohde viscometer.For liquid-crystal mixtures ZLI-2293, ZLI-4792 and MLC-6608, allproducts from Merck KGaA, Darmstadt, Germany, the rotational viscosityvalues determined at 20° C. are 161 mPa·s, 133 mPa·s and 186 mPa·srespectively, and the flow viscosity values (ν) are 21 mm²·s⁻¹, 14mm²·s⁻¹ and 27 mm²·s⁻¹, respectively.

The dispersion of the materials may for practical purposes beconveniently characterized in the following way, which is usedthroughout this application unless explicitly stated otherwise. Thevalues of the birefringence are determined at a temperature of 20° C. atseveral fixed wavelengths using a modified Abbé refractometer withhomeotropically aligning surfaces on the sides of the prisms in contactwith the material. The birefringence values are determined at thespecific wavelength values of 436 nm (respective selected spectral lineof a low pressure mercury lamp), 589 nm (sodium “D” line) and 633 nm(wavelength of a HE-Ne laser (used in combination with anattenuator/diffusor in rder to prevent damage to the eyes of theobservers. In the following table Δn is given at 589 nm and Δ(Δn) isgiven as Δ(Δn)=Δn(436 nm)−Δn(633 nm).

The following symbols are used, unless explicitly indicated otherwise:

-   V₀ threshold voltage, capacitive [V] at 20° C.,-   n_(e) extraordinary refractive index measured at 20° C. and 589 nm,-   n_(o) ordinary refractive index measured at 20° C. and 589 nm,-   Δn optical anisotropy measured at 20° C. and 589 nm,-   λ wavelength λ [nm],-   Δn(λ) optical anisotropy measured at 20° C. and wavelength λ,-   Δ(Δn) change in optical anisotropy defined as:    -   Δn(20° C., 436 nm)−Δn(20° C., 633 nm),-   Δ(Δn*) “relative change in optical anisotropy” defined as:    -   Δ(Δn)/Δn(20° C.,589 nm),-   ∈_(⊥) dielectric susceptibility perpendicular to the director at    20° C. and 1 kHz,-   ∈_(∥) dielectric susceptibility parallel to the director at 20° C.    and 1 kHz,-   Δ∈ dielectric anisotropy at 20° C. and 1 kHz,-   T(N,I) or cl.p.clearing point [° C.],-   ν flow viscosity measured at 20° C. [mm²·s⁻¹],-   γ₁ rotational viscosity measured at 20° C. [mPa·s],-   k₁₁ elastic constant, “splay” deformation at 20° C. [pN],-   k₂₂ elastic constant, “twist” deformation at 20° C. [pN],-   k₃₃ elastic constant, “bend” deformation at 20° C. [pN],-   LTS low-temperature stability of the phase, determined in test    cells,-   VHR voltage holding ratio,-   ΔVHR decrease in the voltage holding ratio, and-   S_(rel) relative stability of the VHR,

The following examples explain the present invention without limitingit. However, they show the person skilled in the art preferred mixtureconcepts with compounds preferably to be employed and the respectiveconcentrations thereof and combinations thereof with one another. Inaddition, the examples illustrate the properties and propertycombinations that are accessible.

For the present invention and in the following examples, the structuresof the liquid-crystal compounds are indicated by means of acronyms, withthe transformation into chemical formulae taking place in accordancewith Tables A to C below. All radicals C_(n)H_(2n+1), C_(m)H_(2m+1) andC_(l)H_(2l+1) or C_(n)H_(2n), C_(m)H_(2m) and C_(l)H_(2l) arestraight-chain alkyl radicals or alkylene radicals, in each case havingn, m and l C atoms respectively. Preferably n, m and l are independentlyof each other 1, 2, 3, 4, 5, 6, or 7. Table A shows the codes for thering elements of the nuclei of the compound, Table B lists the bridgingunits, and Table C lists the meanings of the symbols for the left- andright-hand end groups of the molecules. The acronyms are composed of thecodes for the ring elements with optional linking groups, followed by afirst hyphen and the codes for the left-hand end group, and a secondhyphen and the codes for the right-hand end group. Table D showsillustrative structures of compounds together with their respectiveabbreviations.

TABLE A Ring elements C

D

A

P

G

U

Y

P(F,Cl)Y

np

n3f

th

DI

AI

GI

UI

P(Cl,F)Y

nN3fl

thl

tH2f

o2f

dh

K

L

F

tH2f1

o2f1

KI

LI

FI

TABLE B Bridging units E —CH₂—CH₂— V —CH═CH— T —C≡C— W —CF₂—CF₂— B—CF═CF— Z —CO—O— ZI —O—CO— X —CF═CH— XI —CH═CF— O —CH₂—O— OI —O—CH₂— Q—CF₂—O— QI —O—CF₂—

TABLE C End groups On the left individually or in combination On theright individually or in combination -n- C_(n)H_(2n+1)— -n—C_(n)H_(2n+1) -nO- C_(n)H_(2n+1)—O— -nO —O—C_(n)H_(2n+1) -V- CH₂=CH— -V—CH═CH₂ -nV- C_(n)H_(2n+1)—CH=CH— -nV —C_(n)H_(2n)—CH=CH₂ -Vn-CH₂═CH—C_(n)H_(2n)— -Vn —CH═CH—C_(n)H_(2n+1) -nVm-C_(n)H_(2n+1)—CH═CH—C_(m)H_(2m)— -nVm —C_(n)H_(2n)—CH═CH—C_(m)H_(2m+1)-N- N≡C— -N —C≡N -S- S═C═N— -S —N═C═S -F- F- -F -F -CL- Cl— -CL —Cl -M-CFH₂— -M —CFH₂ -D- CF₂H— -D —CF₂H -T- CF₃— -T —CF₃ -MO- CFH₂O— -OM—OCFH₂ -DO- CF₂HO— -OD —OCF₂H -TO- CF₃O— -OT —OCF₃ -A- H—C≡C— -A —C≡C—H-nA- C_(n)H_(2n+1)—C≡C— -An —C≡C—C_(n)H_(2n+1) -NA- N≡C—C≡C— -AN—C≡C—C≡N On the left only in combination On the right only incombination - . . . n . . . - —C_(n)H_(2n)— - . . . n . . .—C_(n)H_(2n)— - . . . M . . . - —CFH— - . . . M . . . —CFH— - . . . D .. . - —CF₂— - . . . D . . . —CF₂— - . . . V . . . - —CH═CH— - . . . V .. . —CH═CH— - . . . Z . . . - —CO—O— - . . . Z . . . —CO—O— - . . . ZI .. . - —O—CO— - . . . ZI . . . —O—CO— - . . . K . . . - —CO— - . . . K .. . —CO— - . . . W . . . - —CF═CF— - . . . W . . . —CF═CF—in which n and m are each integers, and the three dots “ . . . ” areplaceholders for other abbreviations from this table.

Besides the compounds of formula I, the mixtures according to theinvention preferably comprise one or more compounds of the compoundsmentioned below.

The following abbreviations are used:

(n, m and l are, independently of one another, each an integer,preferably 1 to 6, l possibly also 0 and preferably 0 or 2)

TABLE D

CC-n-m

CC-n-Om

CC-n-V

CC-n-Vm

CC-n-mV

CC-n-mVI

CC-V-V

CC-V-mV

CC-V-Vm

CC-Vn-mV

CC-nV-mV

CC-nV-Vm

CC-n-VV

CC-n-VVm

CVC-n-V

CVC-n-Vm

CP-n-m

CP-n-Om

PP-n-m

PP-n-Om

CCP-n-m

CCP-n-Om

CCP-V-m

CCP-nV-m

CCP-Vn-m

CCP-nVm-I

CPP-n-m

CGP-n-m

PGP-n-m

PGP-n-mV

PGP-n-mVI

CCZPC-n-m

CPPC-n-m

CGPC-n-m

CPGP-n-m

CY-V-n

CY-V-On

CY-nV-m

CY-nV-Om

CY-Vn-m

CY-Vn-Om

CY-nVm-I

CY-nVm-OI

PY-V-n

PY-V-On

PY-nV-m

PY-nV-Om

PY-Vn-m

PY-Vn-Om

PY-nVm-I

PY-nVm-OI

CCY-V-n

CCY-V-On

CCY-nV-m

CCCY-nV-Om

CCY-Vn-m

CCY-Vn-Om

CCY-nVm-I

CCY-nVm-OI

CPY-V-n

CPY-V-On

CPY-nV-m

CPY-nV-Om

CPY-Vn-m

CPY-Vn-Om

CPY-nVm-I

CPY-nVm-OI

CY-n-m

CY-n-Om

CVY-n-m

CVY-V-n

CZY-n-Om

COY-n-m

COY-n-Om

PY-n-m

PY-n-Om

Y-n-m

Y-n-Om

Y-nO-Om

CCY-n-m

CCY-n-Om

CCY-n-mOI

CCZY-n-Om

CCOY-n-m

CCOY-n-Om

CPY-n-m

CPY-n-Om

PYP-n-m

CP(F,Cl)-n-Om

CLY-n-m

CLY-n-Om

CK-n-F

PPGU-n-F

Table E shows chiral dopants which are preferably employed in themixtures according to the invention.

TABLE E

C 15

CB 15

CM 21

R S-811/S-811

CM 44

CM 45

CM 47

CN

R-1011/S-1011

R-2011/S-2011

R-3011/S-3011

R-4011/S-4011

R-5011/S-5011

In a preferred embodiment of the present invention, the media accordingto the invention comprise one or more compounds selected from the groupof the compounds from Table E.

Table F shows stabilisers which can preferably be employed in themixtures according to the invention in addition to the compounds offormula I. The parameter n here denotes an integer in the range from 1to 12. In particular, the phenol derivatives shown can be employed asadditional stabilisers since they act as antioxidants.

TABLE F

In a preferred embodiment of the present invention, the media accordingto the invention comprise one or more compounds selected from the groupof the compounds from Table F, in particular one or more compoundsselected from the group of the compounds of the following four formulae

EXAMPLES

The following examples explain the present invention without restrictingit in any way. However, the physical properties make it clear to theperson skilled in the art what properties can be achieved and in whatranges they can be modified. In particular, the combination of thevarious properties which can preferably be achieved is thus well definedfor the person skilled in the art.

Comparative Example 1

The following mixture (C-1) is prepared and investigated.

Mixture C-1 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 21.0 2 CY-5-O2 4.5 3 CCY-3-O1 11.5 4 CCY-3-O2 7.5 5CLY-3-O2 4.5 6 CLY-3-O3 3.0 7 CPY-2-O2 4.5 8 CPY-3-O2 4.5 9 PYP-2-4 4.510 CC-3-V 33.5 11 CCP-V-1 1.0 Σ 100.0 Physical properties T (N, I) =74.0° C. n_(e) (20° C., 589 nm) = 1.5736 Δn (20° C., 589 nm) = 0.0931ε_(⊥) (20°, 1 kHz) = 7.5 Δε (20°, 1 kHz) = −3.8 γ₁ (20° C.) = 93 mPa · sk₁₁ (20° C.) = 12.5 pN k₃₃ (20° C.) = 14.9 pN V₀ (20° C.) = 2.08 V

Mixture C-1 is characterized by a relatively large wavelength dispersionof the birefringence, which is

Δ(Δn)=Δn(20° C., 436 nm)−Δn(20° C.,633 nm)=0.0112, and thus rather high.Here the accuracy of the value of Δ(Δn) has to be taken as about+/−0.0004, i.e. double the value of the individual Δn-values.

Example 1

The following mixture (M-1) is prepared and investigated.

Mixture M-1 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 25.0 2 CY-5-O2 19.0 3 CCY-3-O2 4.0 4 CLY-3-O2 5.0 5CLY-3-O3 7.0 6 CC-V-V1 14.0 7 CCP-V-1 18.0 8 CCP-V2-1 8.0 Σ 100.0Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) = 1.5777Δn (20° C., 589 nm) = 0.0939 ε_(⊥) (20°, 1 kHz) = 7.5 Δε (20°, 1 kHz) =−3.8 γ₁ (20° C.) = 115 mPa · s k₁₁ (20° C.) = 12.8 pN k₃₃ (20° C.) =16.4 pN V₀ (20° C.) = 2.19 V

Mixture M-1 is characterized by a comparatively small wavelengthdispersion of the birefringence, which is only Δ(Δn)=Δn(20° C., 436nm)−Δn(20° C., 633 nm)=0.0092.

Example 2

The following mixture (M-2) is prepared and investigated.

Mixture M-2 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 24.0 2 CY-5-O2 18.0 3 CCY-3-O2 4.0 4 CLY-3-O2 7.5 5CLY-3-O3 7.0 6 CC-1V-V1 10.0 7 CC-3-V 9.5 8 CCP-V-1 20.0 Σ 100.0Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) = 1.5750Δn (20° C., 589 nm) = 0.0932 ε_(⊥) (20°, 1 kHz) = 7.5 Δε (20°, 1 kHz) =−3.9 γ₁ (20° C.) = 111 mPa · s k₁₁ (20° C.) = 13.3 pN k₃₃ (20° C.) =17.2 pN V₀ (20° C.) = 2.23 V

Mixture M-2 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0086.

Example 3

The following mixture (M-3) is prepared and investigated.

Mixture M-3 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 24.0 2 CY-5-O2 18.0 3 CCY-3-O2 4.0 4 CLY-3-O3 9.0 5CLY-3-O2 5.0 6 CC-2V-V2 10.0 7 CC-3-V 8.0 8 CCP-V-1 18.0 9 CCP-V2-1 4.0Σ 100.0 Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) =1.5741 Δn (20° C., 589 nm) = 0.0918 ε_(⊥) (20°, 1 kHz) = 7.5 Δε (20°, 1kHz) = −3.8 γ₁ (20° C.) = 111 mPa · s k₁₁ (20° C.) = 12.9 pN k₃₃ (20°C.) = 15.5 pN V₀ (20° C.) = 2.14 V

Mixture M-3 is characterized by a very small wavelength dispersion ofthe birefringence, which is even only Δ(Δn)=0.0082.

Example 4

The following mixture (M-4) is prepared and investigated.

Mixture M-4 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 24.0 2 CY-5-O2 18.0 3 CCY-3-O1 5.0 4 CCY-3-O2 8.0 5CCY-3-O3 8.0 6 CC-3-VV 25.0 7 CC-3-V 5.0 8 CCP-V-1 7.0 Σ 100.0 Physicalproperties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) = 1.5706 Δn (20°C., 589 nm) = 0.0921 ε_(⊥) (20°, 1 kHz) = 7.6 Δε (20°, 1 kHz) = −3.8 γ₁(20° C.) = 106 mPa · s k₁₁ (20° C.) = 12.6 pN k₃₃ (20° C.) = 16.3 pN V₀(20° C.) = 2.19 V

Mixture M-4 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0087.

Example 5

The following mixture (M-5) is prepared and investigated.

Mixture M-5 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 22.0 2 CY-5-O2 18.0 3 CCY-3-O2 12.0 4 CLY-3-O3 12.0 5CC-3-VV 27.0 6 CC-3-V 9.0 Σ 100.0 Physical properties T (N, I) = 74.0°C. n_(e) (20° C., 589 nm) = 1.5700 Δn (20° C., 589 nm) = 0.0927 ε_(⊥)(20°, 1 kHz) = 7.7 Δε (20°, 1 kHz) = −3.9 γ₁ (20° C.) = 102 mPa · s k₁₁(20° C.) = 13.0 pN k₃₃ (20° C.) = 16.0 pN V₀ (20° C.) = 2.15 V

Mixture M-5 is characterized by a relatively small wavelength dispersionof the birefringence, which is only Δ(Δn)=0.0094.

Example 6

The following mixture (M-6) is prepared and investigated.

Mixture M-6 Composition Compound Concentration /% No. Abbreviation byweight 1 CY-3-O2 24.0 2 CY-5-O2 18.0 3 CCY-3-O1 5.0 4 CLY-3-O2 6.0 5CLY-3-O3 6.0 6 CVC-3-V 14.0 7 CCP-V-1 22.0 8 CCP-V2-1 5.0 Σ 100.0Physical properties T (N, I) = 75.0° C. n_(e) (20° C., 589 nm) = 1.5760Δn (20° C., 589 nm) = 0.0924 ε_(⊥) (20°, 1 kHz) = 7.4 Δε (20°, 1 kHz) =−3.7 γ₁ (20° C.) = 118 mPa · s k₁₁ (20° C.) = 12.2 pN k₃₃ (20° C.) =15.6 pN V₀ (20° C.) = 2.18 V

Mixture M-6 is characterized by a very small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0083.

Example 7

The following mixture (M-7) is prepared and investigated.

Mixture M-7 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 18.0 2 CY-5-O2 17.0 3 CCY-3-O1 4.0 4 CLY-3-O2 12.0 5CLY-3-O3 7.0 6 PY-3-O2 2.0 7 CC-V-V1 23.0 8 CCP-V-1 17.0 Σ 100.0Physical properties T (N, I) = 75.0° C. n_(e) (20° C., 589 nm) = 1.5789Δn (20° C., 589 nm) = 0.0955 ε_(⊥) (20°, 1 kHz) = 7.4 Δε (20°, 1 kHz) =−3.8 γ₁ (20° C.) = 108 mPa · s k₁₁ (20° C.) = 12.9 pN k₃₃ (20° C.) =16.4 pN V₀ (20° C.) = 2.26 V

Mixture M-7 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0090.

Example 8

The following mixture (M-8) is prepared and investigated.

Mixture M-8 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 20.0 2 CY-5-O2 17.0 3 CCY-3-O1 4.0 4 CLY-3-O2 20.0 5CLY-3-O3 6.0 6 CC-V-V1 14.0 7 CCP-V-1 17.0 Σ 100.0 Physical properties T(N, I) = 78.5° C. n_(e) (20° C., 589 nm) = 1.5786 Δn (20° C., 589 nm) =0.0957 ε_(⊥) (20°, 1 kHz) = 7.7 Δε (20°, 1 kHz) = −4.0 γ₁ (20° C.) = 116mPa · s k₁₁ (20° C.) = 13.6 pN k₃₃ (20° C.) = 17.7 pN V₀ (20° C.) = 2.22V

Mixture M-8 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0089.

Example 9

The following mixture (M-9) is prepared and investigated.

Mixture M-9 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 24.0 2 CY-3-O4 4.0 3 CY-5-O2 12.0 4 CCY-3-O1 6.0 5CLY-3-O2 9.0 6 CLY-3-O3 7.0 7 PY-3-O2 1.0 8 CC-1V-V1 8.0 9 CC-3-V 10.010  CCP-V-1 19.0 Σ 100.0 Physical properties T (N, I) = 74.5° C. n_(e)(20° C., 589 nm) = 1.5767 Δn (20° C., 589 nm) = 0.0942 ε_(⊥) (20°, 1kHz) = 7.8 Δε (20°, 1 kHz) = −4.1 γ₁ (20° C.) = 120 mPa · s k₁₁ (20° C.)= 13.1 pN k₃₃ (20° C.) = 16.8 pN V₀ (20° C.) = 2.14 V

Mixture M-9 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0089.

Example 10

The following mixture (M-10) is prepared and investigated.

Mixture M-10 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 10.0 2 CY-3-O4 8.0 3 CY-5-O2 8.0 4 CLY-2-O4 10.0 5CLY-3-O2 10.0 6 CLY-3-O3 10.0 7 PY-3-O2 3.0 8 CC-1V-V1 21.0 9 CC-3-V20.0 Σ 100.0 Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589nm) = 1.5695 Δn (20° C., 589 nm) = 0.0913 ε_(⊥) (20°, 1 kHz) = 7.0 Δε(20°, 1 kHz) = −3.6 γ₁ (20° C.) = 97 mPa · s k₁₁ (20° C.) = 14.3 pN k₃₃(20° C.) = 17.3 pN V₀ (20° C.) = 2.32 V

Mixture M-10 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0085.

Example 11

The following mixture (M-11) is prepared and investigated.

Mixture M-11 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 20.0 2 CY-5-O2 18.0 3 CCY-3-O2 2.0 4 CLY-3-O2 9.0 5CLY-3-O3 5.0 6 CC-2V-V2 12.0 7 CC-3-V 4.0 8 CCP-V-1 18.0 9 CCP-V2-1 6.0Σ 100.0 Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) =1.5755 Δn (20° C., 589 nm) = 0.0928 ε_(⊥) (20°, 1 kHz) = 7.7 Δε (20°, 1kHz) = −3.8 γ₁ (20° C.) = 113 mPa · s k₁₁ (20° C.) = 12.9 pN k₃₃ (20°C.) = 15.4 pN V₀ (20° C.) = 2.13 V

Mixture M-11 is characterized by a rather small wavelength dispersion ofthe birefringence, which is only Δ(Δn)=0.0085.

Example 12

The following mixture (M-12) is prepared and investigated.

Mixture M-12 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 27.0 2 CY-5-O2 13.0 3 CLY-3-O2 15.0 4 CLY-3-O3 8.0 5CC-3-VV 18.0 6 CC-3-V 10.0 7 CCP-V-1 95.0 Σ 100.0 Physical properties T(N, I) = 76.0° C. n_(e) (20° C., 589 nm) = 1.5766 Δn (20° C., 589 nm) =0.0962 ε_(⊥) (20°, 1 kHz) = 7.8 Δε (20°, 1 kHz) = −4.0 γ₁ (20° C.) = 106mPa · s k₁₁ (20° C.) = 13.3 pN k₃₃ (20° C.) = 16.4 pN V₀ (20° C.) = 2.14V

Mixture M-12 is characterized by a relatively small wavelengthdispersion of the birefringence, which is Δ(Δn)=0.0106.

Example 13

The following mixture (M-13) is prepared and investigated.

Mixture M-13 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 20.0 2 CY-5-O2 18.0 3 CCY-3-O2 5.0 4 CLY-3-O2 9.0 5CLY-3-O3 5.0 6 PY-3-O2 3.0 7 CC-3-VV 17.0 7 CC-3-V 11.0 8 CCP-V-1 8.0 Σ100.0 Physical properties T (N, I) = 74.0° C. n_(e) (20° C., 589 nm) =1.5757 Δn (20° C., 589 nm) = 0.0960 ε_(⊥) (20°, 1 kHz) = 7.8 Δε (20°, 1kHz) = −4.0 γ₁ (20° C.) = 109 mPa · s k₁₁ (20° C.) = 13.2 pN k₃₃ (20°C.) = 15.8 pN V₀ (20° C.) = 2.13 V

Mixture M-13 is characterized by a relatively small wavelengthdispersion of the birefringence, which is Δ(Δn)=0.0103.

Example 14

The following mixture (M-14) is prepared and investigated.

Mixture M-14 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 20.0 2 CY-5-O2 18.0 3 CCY-3-O3 5.0 4 CCY-5-O2 4.0 5CLY-3-O2 9.0 6 CLY-3-O3 5.0 7 PY-3-O2 3.0 8 CC-3-VV 17.0 9 CC-3-V 11.010  CCP-V-1 8.0 Σ 100.0 Physical properties T (N, I) = 73.5° C. n_(e)(20° C., 589 nm) = 1.5750 Δn (20° C., 589 nm) = 0.0924 ε_(⊥) (20°, 1kHz) = 7.4 Δε (20°, 1 kHz) = −4.0 γ₁ (20° C.) = 108 mPa · s k₁₁ (20° C.)= 13.0 pN k₃₃ (20° C.) = 15.8 pN V₀ (20° C.) = 2.11 V

Mixture M-14 is characterized by a comparatively small wavelengthdispersion of the birefringence, which is only Δ(Δn)=0.0097.

Example 15

The following mixture (M-15) is prepared and investigated.

Mixture M-15 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 19.0 2 CY-5-O2 20.0 3 CLY-3-O2 14.0 4 CLY-3-O3 12.0 5CC-3-VV 24.0 6 CC-3-V 11.0 Σ 100.0 Physical properties T (N, I) = 75.5°C. n_(e) (20° C., 589 nm) = 1.5736 Δn (20° C., 589 nm) = 0.0956 ε_(⊥)(20°, 1 kHz) = 7.8 Δε (20°, 1 kHz) = −4.0 γ₁ (20° C.) = 104 mPa · s k₁₁(20° C.) = 13.6 pN k₃₃ (20° C.) = 16.2 pN V₀ (20° C.) = 2.11 V

Mixture M-15 is characterized by a comparatively small wavelengthdispersion of the birefringence, which is only Δ(Δn)=0.0098.

Example 16

The following mixture (M-16) is prepared and investigated.

Mixture M-16 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 17.5 2 CCY-3-O1 &.0 3 CCY-3-O2 10.0 4 CCY-5-O2 5.0 5CLY-3-O2 6.0 6 CLY-3-O3 6.5 7 Y-4O-O4V 12.0 8 CC-3-VV 35.0 9 CC-3-V 3.0Σ 100.0 Physical properties T (N, I) = 75.5° C. n_(e) (20° C., 589 nm) =1.5718 Δn (20° C., 589 nm) = 0.0943 ε_(⊥)(20°, 1 kHz) = 8.2 Δε (20°, 1kHz) = −4.1 γ₁ (20° C.) = 94 mPa · s k₁₁ (20° C.) = 12.9 pN k₃₃ (20° C.)= 16.0 pN V₀ (20° C.) = 2.10 V

Mixture M-16 is characterized by a relatively small wavelengthdispersion of the birefringence, which is Δ(Δn)=0.0105.

Example 17

The following mixture (M-17) is prepared and investigated.

Mixture M-17 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 9.0 2 CCY-2-O2 10.0 3 CCY-3-O1 14.0 4 CLY-3-O2 14.0 5PY-1-O4 5.0 6 PY-3-O2 5.0 7 PY-4-O2 5.0 8 CC-3-VV 7.0 9 CC-3-V 31.0 Σ100.0 Physical properties T (N, I) = 77.5° C. n_(e) (20° C., 589 nm) =1.5773 Δn (20° C., 589 nm) = 0.0957 ε_(⊥) (20°, 1 kHz) = 7.4 Δε (20°, 1kHz) = −3.7 γ₁ (20° C.) = 97 mPa · s k₁₁ (20° C.) = 13.7 pN k₃₃ (20° C.)= 15.6 pN V₀ (20° C.) = 2.16 V

Example 18

The following mixture (M-18) is prepared and investigated.

Mixture M-18 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 22.0 2 CY-5-O2 15.0 3 CLY-3-O2 14.0 4 CLY-3-O3 5.0 5CC-3-VV 31.0 6 CC-3-V 13.0 Σ 100.0 Physical properties T (N, I) = 72.5°C. n_(e) (20° C., 589 nm) = 1.5700 Δn (20° C., 589 nm) = 0.0927 ε_(⊥)(20°, 1 kHz) = 6.9 Δε (20°, 1 kHz) = −3.2 γ₁ (20° C.) = 84 mPa · s k₁₁(20° C.) = 13.0 pN k₃₃ (20° C.) = 16.2 pN V₀ (20° C.) = 2.37 V

Example 19

The following mixture (M-19) is prepared and investigated.

Mixture M-19 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 10.0 2 CY-3-O4 8.0 3 CY-5-O2 8.0 4 CLY-2-O4 10.0 5CLY-3-O2 7.0 6 CLY-3-O3 10.0 7 PY-3-O2 5.0 8 CC-3-VV 6.0 9 CC-1V-V1 21.010  CC-3-V 15.0 Σ 100.0 Physical properties T (N, I) = 73.0° C. n_(e)(20° C., 589 nm) = 1.5728 Δn (20° C., 589 nm) = 0.0942 ε_(⊥) (20°, 1kHz) = 7.0 Δε (20°, 1 kHz) = −3.5 γ₁ (20° C.) = 97 mPa · s k₁₁ (20° C.)= 14.2 pN k₃₃ (20° C.) = 17..2 pN V₀ (20° C.) = 2.35 V

Example 20

The following mixture (M-20) is prepared and investigated.

Mixture M-20 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 22.0 2 CY-5-O2 15.0 3 CLY-3-O2 14.0 4 CLY-3-O3 5.0 5CC-3-VV 20.0 6 CC-3-VV1 7.0 7 CC-3-V 17.0 Σ 100.0 Physical properties T(N, I) = 72.5° C. n_(e) (20° C., 589 nm) = 1.5690 Δn (20° C., 589 nm) =0.0917 ε_(⊥) (20°, 1 kHz) = 6.9 Δε (20°, 1 kHz) = −3.2 γ₁ (20° C.) =t.b.d. mPa · s k₁₁ (20° C.) = t.b.d. pN k₃₃ (20° C.) = t.b.d. pN V₀ (20°C.) = t.b.d. V Note: t.b.d.: to be determined.

Example 21

The following mixture (M-21) is prepared and investigated.

Mixture M-21 Composition Compound Concentration/ No. Abbreviation % byweight 1 CY-3-O2 27.0 2 CY-5-O2 13.0 3 CLY-3-O2 15.0 4 CLY-3-O3 8.0 5CC-3-VV 9.0 6 CC-3-VV1 6.0 7 CC-3-V 13.0 8 CCP-V-1 9.0 Σ 100.0 Physicalproperties T (N, I) = 76.5° C. n_(e) (20° C., 589 nm) = 1.5759 Δn (20°C., 589 nm) = 0.0955 ε_(⊥) (20°, 1 kHz) = 7.8 Δε (20°, 1 kHz) = −4.0 γ₁(20° C.) = t.b.d. mPa · s k₁₁ (20° C.) = t.b.d. pN k₃₃ (20° C.) = t.b.d.pN V₀ (20° C.) = t.b.d. V Note: t.b.d.: to be determined.

Mixtures M-17 to M-21 are characterized by a comparatively small or atleast a relatively small wavelength dispersion of the birefringence,similar to those observed for the previous examples.

1. Liquid-crystalline medium comprising a) one or more compounds offormula I

in which a, b and c independently of each other denote an integer of 0or 1, (a+b+c) is 1, 2 or 3, R¹¹ and R¹² independently of each otherdenote H or alkyl with 1 to 5 C atoms, and b) one or more compoundsselected from the group of compounds of the formulae II and III

in which R²¹ denotes an unsubstituted alkyl radical having 1 to 7 Catoms, an unsubstituted alkenyl radical having 2 to 7 C atoms or anunsubstituted alkoxy radical having 1 to 6 C atoms, R²² denotes anunsubstituted alkyl radical having 1 to 7 C atoms, an unsubstitutedalkoxy radical having 1 to 6 C atoms or an unsubstituted alkenyloxyradical having 2 to 6 C atoms, and I denotes 0 or 1, R³¹ denotes anunsubstituted alkyl radical having 1 to 7 C atoms or an unsubstitutedalkenyl radical having 2 to 7 C atoms, R³² denotes an unsubstitutedalkyl radical having 1 to 7 C atoms, an unsubstituted alkoxy radicalhaving 1 to 6 C atoms or an unsubstituted alkenyloxy radical having 2 to6 C atoms, and

denotes


2. Medium according to claim 1, characterised in that it comprises oneor more compounds of formula I selected from the group of the compoundsof the formulae I-1 to I-3

in which the parameters have the meanings indicated in claim
 1. 3.Medium according to claim 1, characterised in that it comprises one ormore compounds of formula IV

in which R⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 Catoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, and R⁴²denotes an unsubstituted alkyl radical having 1 to 7 C atoms or anunsubstituted alkoxy radical having 1 to 6 C atoms, 4.Liquid-crystalline medium according to claim 1, characterised in that itcomprises one or more compounds of formula V

in which R⁵¹ and R⁵², independently of one another, have one of themeanings given for R²¹ and R²² in claim 1,

if present, each, independently of one another, denote

Z⁵¹ to Z⁵³ each, independently of one another, denote —CH₂—CH₂—,—CH₂—O—, —CH═CH—, —C≡C—, —COO— or a single bond, and i and j each,independently of one another, denote 0 or
 1. 5. Liquid-crystallinemedium according to claim 1, characterised in that it one or morecompounds of formula II and/or III selected from the group of thecompounds of the formulae II-1, II-2, III-1 and III-2

in which the parameters have the respective meanings given in claim 1.6. Liquid-crystalline medium according to claim 5, characterised in thatit comprises one or more compounds of formula II selected from the groupof the compounds of the formulae II-1 and II-2


7. Medium according to claim 1, characterised in that the totalconcentration of the compounds of formula I in the medium as a whole is5% or more to 35% or less.
 8. Medium according to claim 1, characterisedin that the total concentration of the compounds of formula II in themedium as a whole is 25% or more to 45% or less.
 9. Medium according toclaim 1, characterised in that it additionally comprises one or morechiral compounds.
 10. Electro-optical display or electro-opticalcomponent, characterised in that it comprises a liquid-crystallinemedium according to claim
 1. 11. Display according to claim 10,characterised in that it is based on the VA-, ECB- IPS- or FFS mode. 12.Display according to claim 10, characterised in that it contains anactive-matrix addressing device.
 13. Use of a medium according to claim1 in an electro-optical display or in an electro-optical component. 14.Display according to claim 10, characterised in that it is a mobiledisplay.
 15. Process for the preparation of a liquid-crystalline mediumaccording to claim 1, characterised in that one or more compounds offormula I are mixed with one or more compounds of formula II and/or oneor more compounds selected from the group of the compounds of theformulae III, IV and V.